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Background: Thinopyrum intermedium (Host) Barkworth & D.R. Dewey, or intermediate wheat grass (IWG), is being developed as the first widely-available perennial grain candidate. However, because the crop is still in development, grain yields are lower than those of traditional cereals. Utilization of its non-grain biomass (e.g. for biofuel production and as a source of fine chemicals) would increase the economic value of its cultivation. The present study provides a structural characterization of the lignin and cell wall carbohydrates in IWG biomass and qualitative profiling of biomass extractives and compares them to those of annual wheat (Triticum aestivum) biomass grown in the same location and growing season., Results: The monosaccharide composition and ester-linked phenolic acid contents of vegetative biomass material from annual wheat and IWG were similar. IWG vegetative biomass is rich in feruloylated arabinoxylans (AX) with a very low substitution rate, whereas the AX from IWG bran have a slightly higher substitution rate. The structure of IWG lignin was investigated using both the quantitative derivatization followed by reductive cleavage method and 2D-NMR analysis, revealing an H:G:S lignin that incorporates tricin and is acylated with coumaric acid and smaller amounts of ferulates. IWG and wheat extractives contained fatty acids, various free phenolic compounds (tricin, monolignols and phenolic acids), phenolic conjugates and phytosterols., Conclusion: The present study provides firm support for the further exploration of T. intermedium biomass as a carbohydrate feedstock (e.g, abundant in lightly substituted AX and cellulose polymers) for biofuel production and source of high-value fine chemicals, such as tricin. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

Summary: To what degree can the lignin subunits in a monocot be derived from monolignol ferulate (ML‐FA) conjugates? This simple question comes with a complex set of variables. Three potential requirements for optimizing ML‐FA production are as follows: (1) The presence of an active FERULOYL‐CoA MONOLIGNOL TRANSFERASE (FMT) enzyme throughout monolignol production; (2) Suppression or elimination of enzymatic pathways competing for monolignols and intermediates during lignin biosynthesis; and (3) Exclusion of alternative phenolic compounds that participate in lignification. A 16‐fold increase in lignin‐bound ML‐FA incorporation was observed by introducing an AsFMT gene into Brachypodium distachyon. On its own, knocking out the native p‐COUMAROYL‐CoA MONOLIGNOL TRANSFERASE(BdPMT) pathway that competes for monolignols and the p‐coumaroyl‐CoA intermediate did not change ML‐FA incorporation, nor did partial loss of CINNAMOYL‐CoA REDUCTASE1 (CCR1) function, which reduced metabolic flux to monolignols. However, stacking AsFMT into the Bdpmt‐1 mutant resulted in a 32‐fold increase in ML‐FA incorporation into lignin over the wild‐type level. [ABSTRACT FROM AUTHOR]

The industrial production of palm oil concurrently generates a substantial amount of empty fruit bunch (EFB) fibers that could be used as a feedstock in a lignocellulose-based biorefinery. Lignin byproducts generated by this process may offer opportunities for the isolation of value-added products, such as p-hydroxybenzoate ( pBz), to help offset operating costs. Analysis of the EFB lignin by nuclear magnetic resonance (NMR) spectroscopy clearly revealed the presence of bound acetate and pBz, with saponification revealing that 1.1 wt% of the EFB was pBz; with a lignin content of 22.7 %, 4.8 % of the lignin is pBz that can be obtained as a pure component for use as a chemical feedstock. Analysis of EFB lignin by NMR and derivatization followed by reductive cleavage (DFRC) showed that pBz selectively acylates the γ-hydroxyl group of S units. This selectivity suggests that pBz, analogously with acetate in kenaf, p-coumarate in grasses, and ferulate in a transgenic poplar augmented with a feruloyl-CoA monolignol transferase (FMT), is incorporated into the growing lignin chain via its γ- p-hydroxybenzoylated monolignol conjugate. Involvement of such conjugates in palm lignification is proven by the observation of novel p-hydroxybenzoylated non-resinol β-β-coupled units in the lignins. Together, the data implicate the existence of p-hydroxybenzoyl-CoA:monolignol transferases that are involved in lignification in the various willows ( Salix spp.), poplars and aspen ( Populus spp., family Salicaceae), and palms (family Arecaceae) that have p-hydroxybenzoylated lignins. Even without enhancing the levels by breeding or genetic engineering, current palm oil EFB 'wastes' should be able to generate a sizeable stream of p-hydroxybenzoic acid that offers opportunities for the development of value-added products derived from the oil palm industry. [ABSTRACT FROM AUTHOR]

Grass lignins contain substantial amounts of p-coumarate ( pCA) that acylate the side-chains of the phenylpropanoid polymer backbone. An acyltransferase, named p-coumaroyl-CoA:monolignol transferase ( Os PMT), that could acylate monolignols with pCA in vitro was recently identified from rice. In planta, such monolignol- pCA conjugates become incorporated into lignin via oxidative radical coupling, thereby generating the observed pCA appendages; however p-coumarates also acylate arabinoxylans in grasses. To test the authenticity of PMT as a lignin biosynthetic pathway enzyme, we examined Brachypodium distachyon plants with altered BdPMT gene function. Using newly developed cell wall analytical methods, we determined that the transferase was involved specifically in monolignol acylation. A sodium azide-generated Bdpmt-1 missense mutant had no (<0.5%) residual pCA on lignin, and BdPMT RNAi plants had levels as low as 10% of wild-type, whereas the amounts of pCA acylating arabinosyl units on arabinoxylans in these PMT mutant plants remained unchanged. pCA acylation of lignin from BdPMT-overexpressing plants was found to be more than three-fold higher than that of wild-type, but again the level on arabinosyl units remained unchanged. Taken together, these data are consistent with a defined role for grass PMT genes in encoding BAHD (BEAT, AHCT, HCBT, and DAT) acyltransferases that specifically acylate monolignols with pCA and produce monolignol p-coumarate conjugates that are used for lignification in planta. [ABSTRACT FROM AUTHOR]

Abstract: The DFRC (Derivatization Followed by Reductive Cleavage) analysis of lignin gives phenylpropanoid (C6–C3 type) degradation products from arylether linkages and can be used to detect lignin specifically from plant tissues, excluding other (poly) phenolic substances. DFRC analysis was employed to investigate the lignin composition in broad-leaves of typical Japanese angiosperms. Many leaves gave both guaiacyl- (G, 3-methoxyphenyl-) and syringyl- (S, 3,5-dimethoxyphenyl-) type degradation products, which indicates the existence of lignin in angiospermous leaves, and the leaf lignin has common structural elements with xylem lignin of the same tree. However, the results sometimes differed among species. Persimmon and cherry leaves revealed only trace amounts of degradation products. These results show the heterogeneous distribution of leaf lignin in angiospermous tree species. The syringyl/guaiacyl ratio of leaf lignin DFRC products was apparently lower than that of xylem lignin, which suggests the role of leaf lignin as a material to reinforce leaf vascular tissue for water conduction, like the low S/G ratio in woody vessel element cells. [Copyright &y& Elsevier]

Lignin is the cell wall component most frequently associated with hardening. Its characterization and quantification are very important to understand the biochemical modifications related to the changes in texture of vegetables such as asparagus ( Asparagus officinalis), in which this organoleptic attribute is a very important quality factor. In this study, asparagus lignin from the basal sections of fresh and stored spears was analyzed using 2 methods, the traditional (Klason lignin) and the recently developed derivatization, followed by reductive cleavage (DFRC) method. The latter is a simple and reproducible technique for lignin characterization based on a degradation procedure that produces analyzable monomers and dimers by cleaving α- and β-aryl ethers in lignins. The primary monomers derived from DFRC degradation of lignins are essentially p-coumaryl peracetate, coniferyl peracetate, and sinapyl peracetate. To evaluate the efficiency of the DFRC method, our investigations have been carried on distinct sample types, including wood (data not shown), straw, and asparagus samples. The results have confirmed that lignin composition is affected by plant nature. It has been found that whereas wood samples mostly contain coniferyl units, plant foods, such as straw and asparagus, contain both coniferyl and guaiacyl units. [ABSTRACT FROM AUTHOR]

The DFRC method was applied to dimeric model compounds of lignin; dehydrodiconiferyl alcohol, syringaresinol, pinoresinol, syringylglycerol-ß-sinapyl ether, and guiacylglycerol-ß-coniferyl ether. Dehydrodiconiferyl alcohol yielded no coniferyl alcohol, but syringaresinol and pinoresinol gave small amounts of corresponding p -hydroxycinnamyl alcohol. In the case of syringaresinol, an acetylated bromo dihydro-(Compound 1, 23%) and tetrahydronaphthalene (Compound 2, 52%) were obtained after acetyl bromide treatment, the first step in the DFRC method. Further, a small amount of sinapyl alcohol diacetate was obtained from compounds 1 and 2 by zinc and successive acetylation treatments. Compound 2 yielded a larger amount of sinapyl alcohol than compound 1. [ABSTRACT FROM AUTHOR]

13C- and deuterium (D)-labeled ferulic acid and sinapic acid ([8-13C, 3-OCD3]-ferulic acid and [8-13C, 3,5-OCD3]-sinapic acid) were administered to robinia (Robinia pseudoacacia L.) shoots. To estimate the distribution of the label from administrated ferulic or sinapic acid, continuous 50-μm-thick tangential sections cut from the cambium of robinia were subjected to lignin chemical analysis by the DFRC method. Labeled ferulic acid was incorporated into guaiacyl and syringyl lignin. The incorporation of labeled ferulic acid into syringyl units was observed only in the later stage of lignification. Labeled sinapic acid was incorporated into syringyl lignin in the early stage and the later stage of lignification. In general, syringyl lignin was deposited in the later stage of cell wall lignification. Thus, the incorporation of sinapic acid to syringyl lignin in the early stage of lignification was abnormal. Taken together, the aromatic ring-modifying reactions (the conversion from guaiacyl to syringyl moiety, including the hydroxylation and methylation) were more important for the regulation of the sinapyl alcohol biosynthesis than the reducing reactions (the reduction of acids to alcohols) in the differentiating xylem. To cite this article: K. Yamauchi, K. Fukushima, C. R. Biologies 327 (2004). [Copyright &y& Elsevier]

The derivatization followed by reductive cleavage (DFRC) method is a well-established tool to characterize the lignin composition of plant materials. However, the application of the original procedure, especially the chromatographic determination of the DFRC monomers, is problematic for low-lignin foods. To overcome these problems a modified sample cleanup and a stable-isotope dilution approach were developed and validated. To quantitate the diacetylated DFRC monomers, their corresponding hexadeuterated analogs were synthesized and used as internal standards. By using the selected-ion monitoring mode, matrix-associated interferences can be minimized resulting in higher selectivity and sensitivity. The modified method was applied to four low-lignin samples. Lignin from carrot fibers was classified as guaiacyl-rich whereas the lignins from radish, pear, and asparagus fibers where classified as balanced lignins (guaiacyl/syringyl ratio=1-2).